This change occurred not in a single season but over time, from the 1960s into the '90s—a gradual but constant shift toward more straight-on, powerful collisions that coincided with players' getting bigger, faster and stronger. The last several generations of NFL players came up playing by a common set of tackling rules. "Lead with your head," says veteran linebacker Nick Barnett, who played eight years in Green Bay and is now with the Bills.
"See what you hit," says Steelers linebacker James Farrior, a 15-year veteran who has won two Super Bowls with Pittsburgh.
"Eyes up, head across, bite the ball," says Patriots fourth-year linebacker Jerod Mayo. "Then bring your hips through and grab cloth in the back. That's old-school, Pepper Johnson--style tackling."
"Low man wins—drive your feet," says Buffalo linebacker Chris Kelsay. "Same set of rules I learned in junior high school."
This head-on technique was at first perceived as safer. "Back in the old days," says Bills coach Chan Gailey, 59, who played quarterback at Florida in the early 1970s, "we had a lot of neck injuries from guys turning their head at impact to use the shoulder." But as the game quickened and headgear became seemingly more protective (a proven fallacy), players began to use the crown of the helmet to deliver heavy blows. Seeing what they hit became seeing what they intended to hit, then lowering their heads at the last moment.
Concurrently the game became faster and more spread out. Running plays had dominated the NFL and college football into the mid-1970s, but rules changes limiting physical pass coverage and schematic innovations helped shift the strategic weight to the passing game. In 1975, NFL teams averaged 27.4 passes and 36.3 runs per game; in 2010 the numbers were 33.7 passes and 27.2 runs. That means less action between the tackles, where the defenders' lines of pursuit are shorter and more compact, and more in the open field, where the ballcarriers become more elusive. "Faster athletes in more space," says Steelers defensive coordinator Dick LeBeau, who played defensive back in the NFL from 1959 to '72 and has been a coach since '73. "The guys with the ball have gotten much better. They're good at deceit, and they have the burst to make you pay for any mistake. So a lot more often you're seeing a tackler just get an arm on [the ballcarrier]." (Coaches do note that young players, even as their tackling skills have declined, possess much more advanced pass-coverage ability.)
Two predominant trends have emerged as the game has changed.
First, conventional tackling skills (securing the ballcarrier and putting him on the ground) have diminished, especially among perimeter defenders—defensive backs and outside linebackers. "We're teaching the same fundamentals we've always taught," says Belichick. "But the young players coming in are more in need of that teaching. Execution of the basic techniques has diminished."
Mike Singletary, the Hall of Fame linebacker who's now a defensive assistant with the Vikings, says, "There's not much focus on individual tackling skills. The focus is on taking the right angle and getting a group of guys to the ball, like a pack of wild dogs. Know where your help is and make sure everybody is running to the ball."
Second, a new type of tackler emerged, one who had almost no tackling technique but a penchant for blowing up receivers and ballcarriers by launching into them, helmet-first. A tackler like Patriots fifth-year safety Brandon Meriweather, whose Black Sunday knockout of Ravens tight end Todd Heap might have been more brutal than Steelers linebacker James Harrison's more publicized shot on Browns wideout Mohamed Massaquoi. Meriweather was taught tackling by his uncle and cousin, who hung a heavy punching bag from a tree in the backyard of Meriweather's home in Apopka, Fla., and told their young student to just hit it.